UN Secretary-General Ban Ki-Moon told reporters at a news conference that "Unless we address the underlying causes of the conflict, another round of violence and vengeance is almost guaranteed."

He said that while Israel had a "duty to protect its citizens" from Hamas rocket attacks, its operation in the Gaza Strip has raised "serious questions" regarding Israel's respect for principles of "distinction and proportionality."

He said that militant activity does not justify putting the lives and safety of innocent civilians at risk. "I have called for an investigation into the repeated shelling of UN facilities" that house civilians, he said, adding that he expected those responsible to be held accountable "for the innocent lives lost and the damage incurred."